During fabrication of semiconductor devices, electron beam lithography is often used to pattern very small high resolution features with very accurate pattern registration. However, many devices are now being formed employing electrically isolated mesa structures. These mesa structures are often separated and isolated by very high resistivity material. Electrically isolated mesas present a very unique problem when employing electron beam lithography.
The very high resistivity material isolating the mesa structures causes a charge to accumulate during the electron beam writing or patterning step. As the accumulated charge in the mesa becomes larger, the electron beam can be deflected resulting in pattern distortion. Distortion of the electron beam degrades both resolution and registration.
It would be highly advantageous, therefore, to remedy the foregoing and other deficiencies inherent in the prior art.
Accordingly, it is an object of the present invention to provide a new and improved method of employing electron beam lithography on very high resistivity substrates.
Another object of the invention is to provide a method of employing electron beam lithography on electrically isolated mesa structures.
A further object of the present invention is to provide a method of employing electron beam lithography on electrically isolated mesa structures while maintaining high resolution and accurate pattern registration.